Transition form factor of γ → 3π in a nonlocal quark model

The transition form factor of a gamma into three pions F3π are studied in a framework of nonlocal chiral quark model. In local limit the result is agreement with chiral perturbative theory and reproduce Wess-Zumino-Witten anomaly. Availability of nonlocality not change a value of transition form factor in chiral limit. On the physical threshold of reaction, the transition form factor F3π is obtained close to the experimental data on account of current mass of quark

Intrinsic multipole moments of non-Gaussian wave packets

The charged wave packets with non-Gaussian spatial profiles are shown to possess intrinsic multipole moments. The magnetic dipole moment and the electric quadrupole moment are found for a wide class of the packets, including the vortex electrons with orbital angular momentum ℓ, the Airy beams, the so-called Schrödinger's cat states, and their generalizations. For the packets with no phase vortices, the electric quadrupole moment is shown to grow quadratically with the packet's width, |Qαβ|∼e⋅σ2⊥, while it is also |ℓ| times enhanced for the vortex beams. For available beams of electron microscopes, these multipole moments are relatively easily adjusted and can be quite large, which affects the packets' electromagnetic fields and also allows one to develop new diagnostic tools for materials science, atomic and molecular physics, nuclear physics, and so forth

Deep inelastic e−τe-\tau and μ−τ\mu-\tau conversion in the NA64 experiment at the CERN SPS

We study the Lepton Flavor Violating (LFV) $e(\mu)-\tau$ conversion in Deep Inelastic Scattering (DIS) of electron (muon) on fixed-target nuclei. Our model-independent analysis is based on the set of the low-energy effective four-fermion LFV operators composed of leptons and quarks with the corresponding mass scales $\Lambda_{k}$ for each operator. Using the estimated sensitivity of the search for this LFV process in events with large missing energy in the NA64 experiment at the CERN SPS, we derive lower limits for $\Lambda_{k}$ and compared them with the corresponding limits existing in the literature. We show that the DIS $e(\mu)-\tau$ conversion is able to provide a plenty of new limits as yet non-existing in the literature. We also analyzed the energy spectrum of the final-state $\tau$ and discussed viability of the observation of this process in the NA64 experiment and ones akin to it. The case of polarized beams and targets is also discussed.Comment: 18 page

The muon g-2: retrospective and future

Soon, new experiments at FNAL and J-PARC will measure the muon anoma-lous magnetic moments with better accuracy than before. From theoretical side, the un-certainty of the standard model prediction is dominated by the hadronic contributions. Current status of the experimental data and theoretical calculations are briefly discussed

Implication of the dark axion portal for the EDM of fermions and dark matter probing with NA64ee, NA64μ\mu, LDMX, \mbox{M}^3, and BaBar

The link between ordinary Standard model (SM) photon and both dark photon and axion like particle (ALP) can be introduced through the dark axion portal coupling. Given the dark axion portal setup, in the present paper we refer the dark photon as the mediator between SM and dark matter (DM) particles, implying that it decays predominantly into pair of DM fermions. Furthermore, we discuss in detail the implication of the dark axion portal scenario for the lepton (electron and muon) fixed target experiments. In particular, for the specific fixed target facility we study the missing energy signatures of the dark photon production followed by its invisible decay into stable DM particles. We investigated the potential to probe dark axion portal vertices with regarding signatures and derive the expected sensitivities of NA64$e$, NA64$\mu$, LDMX and \mbox{M}^3. Moreover, we estimated the expected reach of NA64$e$ from the projected statistics of the $J/\psi$ vector meson invisible decays. We also recasted BaBar monophoton bounds for the specific dark axion portal scenario. In addition, we modified the dark axion portal setup by including in the model both the hadron and lepton specific ALP couplings. As the result, we obtain the bounds on the combination of fermion-specific couplings of ALP from the fixed target experiments. We discuss the implication of the modified dark axion portal scenario for the electric dipole moments (EDM) of SM fermions. In addition, we derived the novel constraints on the combination of the $CP$-violating neutron-specific ALP couplings from the existing bounds on neutron EDM by taking into account the neutron anomalous magnetic moment.Comment: 17 pages, 15 figure

Current status of the muon g-2

The current status of the muon g-2 problem is briefly discussed. We briefly discuss the latest results on the muon g-2 measured in experiment and obtained theoretically within the standard model. Special attention is for the hadronic corrections and in particular the corrections due to the light by light scattering mechanism. For latter we present the results found in the leading in 1=N c approximation with the nonlocal chiral quark model

Lepton flavor violating dark photon

We study possible impact of dark photons on lepton flavor phenomenology. We derive the constraints on non-diagonal dark photon couplings with leptons by analyzing corresponding contributions to lepton anomalous magnetic moments, rare lepton decays and the prospects of fixed-target experiments aiming for search for light dark matter based on missing energy/momentum techniques.Comment: 9 pages, 9 Fig